Mybatis的环境搭建

1.创建maven工程导入mybatis坐标（其他坐标根据需要搜索repository）

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.mystudy</groupId>
    <artifactId>day01_mybatis</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>
    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.12</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.10</version>
        </dependency>
    </dependencies>
</project>

2.创建实体类和DAO接口

• 创建User实体类

package com.itheima.domain;

import java.io.Serializable;
import java.util.Date;

public class User implements Serializable {

    private Integer id;
    private String username;
    private Date birthday;
    private String sex;
    private String address;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", birthday=" + birthday +
                ", sex='" + sex + '\'' +
                ", address='" + address + '\'' +
                '}';
    }
}

• 创建DAO接口

package com.itheima.dao;

import com.itheima.domain.User;

import java.util.List;

/**
 * 用户持久层接口
 */
public interface UserDao {
    /**
     * 查询所有操作
     * @return
     */
    List<User> findAll();
}

3.创建Mybatis主配置文件（SqlMapConfig.xml）

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!-- 配置环境 （主配置文件）-->
    <environments default="mysql">
        <!--配置mysql的环境-->
        <environment id="mysql">
            <!--配置事务的类型-->
            <transactionManager type="JDBC"></transactionManager>
            <!--配置数据源（连接池）-->
            <dataSource type="POOLED">
                <!--配置数据库的连接信息-->
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/studydb"/>
                <property name="username" value="root"/>
                <property name="password" value="961020"/>
            </dataSource>
        </environment>
    </environments>
    <!--指定映射配置文件的位置，映射配置文件指的是每一个dao独立的配置文件路径-->
    <mappers>
        <mapper resource="com/itheima/dao/UserDao.xml"></mapper>
    </mappers>
</configuration>

4.创建映射配置文件（UserDao.xml）

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.dao.UserDao">
    <!--配置查询所有-->
    <select id="findAll">
        select * from User;
    </select>
</mapper>

• • • 注意事项

1.创建UserDao.java和UserDao.xml的命名是为了和小白所学知识保持一致，在Mybatis持久层中操作接口名称和映射文件也叫做：Mapper
  所以：UserDao和UserMapper是一样的
2.在idea闯进目录的时候，和包是不一样的
  包在创建时：com.dao是二级结构
  目录在创建时：com.dao是一级目录
3.mybatis的映射配置文件必须要和dao接口的包结构相同
4.映射配置文件的mapper标签namespace属性的取值必须是dao接口的全限定类名
5.映射配置文件的select的id必须是dao接口的方法名
遵从了3、4、5则不需要再写dao的实现类